Your best bet is to look through the person specification for the role as the questions should be based around that. For a Band 6 role they will probably ask you some clinical questions/scenarios but they may well have a more 'management'-y theme rather than being purely technical, so things which have a safeguarding/equality and diversity/dignity and respect/quality and safety/management of difficult situations and working/communicating with patients and their families in difficult situations could be the kind of things which could come up. So off the top of my head for a critical care role it could be things like how would be you ensure a patients cultural or religious needs are met within a critical care environment and how would you balance any conflict of those needs with the treatment/care plan for them, or how would you manage a conflict about the treatment plan amongst a patients family or between the patients family and the team, for instance.
There will highly likely be some questions around staff management, supervision and training of junior staff, also maybe something around quality/safety improvements, perhaps incident management and reporting, leadership, (MDT) team working and time management/prioritisation. I would have good competency examples prepared for all of these in the STAR(R) model. Even if they phrase a question as more of a scenario 'what would you do' rather than specifically asking you for examples of when you have done this in the past, it is best to be able to evidence everything you say from your own experience.
Of course also have the standard answers ready for why you want the job, your strengths and weaknesses, the trusts values, the NMC code etc etc.
Good luck!